1. Field of the Invention
The present invention relates to an improvement in heat exchange pipes which exhaust flue products from and provides preheated combustion air to a furnace. In particular the present invention relates to an improvement in such heat exchange pipes which are horizontally oriented to extend outside of a building.
2. Prior Art
U.S. Pat. No. 4,262,608 to Jackson shows a blower unit for providing heated combustion air around a furnace through heat exchange pipes with an air intake pipe surrounding a flue products exhaust pipe from the furnace so as to provide heated air around a furnace in a building. One variation described includes heat exchange pipes which are horizontally oriented to extend outside the building. This construction is particularly advantageous where an existing building is to be retrofitted with the blower unit and heat exchange pipes. The blower unit of U.S. Pat. No. 4,262,608 works very well; however, a problem arose in that water condensing in the inner flue products exhaust pipe contained SO.sub.x and other absorbed combustion products from the fuel (natural gas or oil) which are highly corrosive. As a result, the exhaust product pipe could be perforated, thus allowing flue products to escape into the outer air intake pipe which was hazardous. Thus there was a need to solve this problem in a manner which was simple and economical.